1. Field of the Invention
This invention relates to a disk drive suspension comprising a microactuator element of, for example, lead zirconate titanate (PZT).
2. Description of the Related Art
A hard disk drive (HDD) is used in an information processing apparatus, such as a personal computer. The HDD comprises a magnetic disk rotatable about a spindle, a carriage turnable about a pivot, etc. The carriage, which comprises an actuator arm, is configured to be turned transversely relative to tracks about the pivot by a positioning motor, such as a voice coil motor.
A suspension is mounted on the actuator arm. The suspension comprises a load beam, flexure superposed thereon, etc. A slider, which constitutes a magnetic head, is mounted on a gimbal portion formed near the distal end of the flexure. The slider is provided with elements (transducers) for accessing data, that is, for reading or writing data. The load beam, flexure, slider, etc., constitute a head gimbal assembly.
In order to overcome the increase in the recording density of disks, the magnetic head should be more precisely positioned relative to the recording surface of each disk. To attain this, dual-stage-actuator (DSA) suspensions have been developed that combine a positioning motor (voice coil motor) and microactuator element made of a piezoelectric material, such as lead zirconate titanate (PZT).
The distal end of the suspension can be quickly moved by an infinitesimal distance in a sway direction (or transversely relative to tracks) by applying a voltage to and thereby deforming the microactuator element. As disclosed in Jpn. Pat. Appln. KOKAI Publications Nos. 2010-146631 (Patent Document 1) and 2010-218626 (Patent Document 2), moreover, there are also known co-located DSA suspensions in which microactuator elements are mounted on a gimbal portion of a flexure.
FIG. 23 shows frequency response characteristics of a conventional co-located DSA suspension with microactuator elements mounted on a gimbal portion. In FIG. 23, full line S1 represents a frequency response characteristic curve obtained when the gimbal portion is swung by driving the microactuator elements (PZT excitation). Dash-dotted line S2 represents a frequency response characteristic curve obtained when a base portion is caused to vibrate by an exciter so that the gimbal portion is swung (baseplate excitation).
In the example of FIG. 23, the gain is increased as a torsional mode based on PZT excitation is coupled with one based on baseplate excitation at point G1 near 12 kHz, point G2 near 17 kHz, etc. There is a possibility of the amplified vibration adversely affecting the properties of the gimbal portion. If the resonance modes based on the PZT and baseplate excitations are coupled in this manner, the increase of the gain by the coupling can be suppressed by reducing the gain of one of the resonance modes by some means.